Layout/MultilineMethodArgumentLineBreaks False Positive On Multiline Assignment

[jfelchner]

This is a pretty major bug. The Layout/MultilineMethodArgumentLineBreaks cop is throwing errors when an assignment spans multiple lines. I'm assuming because it sees the assignment operator as a "method" (which it technically is but should not be treated like a method call for the purposes of this cop).

Original PR: #6826

/cc @maxh

---

Expected behavior

The following code should not throw an error.

class Thing
  def call
    bar['foo'] = ::Time.zone.at(
                   huh['foo'],
                 )
  end
end

Actual behavior

It throws an error.

Steps to reproduce the problem

See code snippet above.

RuboCop version

0.67.2 (using Parser 2.6.2.1, running on ruby 2.6.2 x86_64-darwin17)

[maxh]

Apologies for delay; didn't get an email for this. Fix: #7072